1. Field of the Invention
The present invention relates to a motorized bicycle and, more particularly, to a motorized bicycle including a manpower driving section and an electromotive driving section and adapted to assist a man-power driving force with an electromotive driving force by driving an electric motor depending on the man-power driving force.
2. Description of Related Art
A conventional motorized bicycle is disclosed in Japanese Unexamined Patent Publication No.5-246378 (1993), which includes a driving system driven by man-power and a driving system driven by an electric motor and is adapted to control the output of the electric motor by detecting a driving force of the man-power driving system, i.e., a pedaling force (a force applied onto pedals).
Specifically, as shown in FIG. 31, the pedaling force, the current of the motor, and the speed of the bicycle are detected by a pedaling force detecting section 201, a motor current detecting section 202 and a bicycle speed detecting section 203, respectively, and these data are inputted into a controller 204, which controls a voltage to be applied to a motor 205. More specifically, the voltage (average voltage) to be applied to the motor 205 is controlled by a switching element or the like, so that the motor 205 generates a torque depending on the detected pedaling force to drive a wheel 207 via a decelerator 206.
If a signal is outputted from the pedaling force detecting section 201 due to a noise in the motorized bicycle when no force is applied to the pedals, however, the motor 205 is erroneously operated. That is, when the motorized bicycle is not pedaled, the output from the pedaling force detecting section 201 fluctuates between zero and a level slightly greater than zero. This causes the motor 205 to be driven and stopped in an unstable manner.
To solve this problem, the motor is adapted to be driven only when the pedaling force exceeds a predetermined threshold. Where the motorized bicycle is designed such that the driving of the motor is stopped when the pedaling force is less than the threshold, however, an assist by the motor is not available when the motorized bicycle is driven with a pedaling force less than the threshold.
Where the motorized bicycle is designed so as to prevent the driving of the motor from being stopped when the pedaling force becomes less than the threshold after the driving of the motor is once started with the pedaling force exceeding the threshold, the aforesaid problem may occur. That is, the motor is driven and stopped in an unstable manner when no pedaling force is applied.
A conventional motorized bicycle of another type is proposed, for example, in Japanese Unexamined Patent Publication No. 4-100790 (1992), which includes a pedaling force sensor for detecting main driving force and a motor current sensor for detecting auxiliary driving force, wherein the output of a motor is controlled on the basis of values detected by these sensors.
However, the outputs of these sensors each include an offset (outputted when no input is applied thereto). The offset fluctuates due to temperature drift, and varies depending on the sensors (even if sensors of the same type are used). Therefore, it is difficult to correct the outputs of these sensors to obtain true detection values.